1. Field of the Invention
The present invention is directed to manufacturing methods. In particular, it deals with ways of assembling solenoid-controlled valves of the type that are pilot-operated.
2. Background Information
Many solenoid-controlled valves are pilot-operated. They include a main valve that would require a large solenoid and a lot of power to operate directly. Rather than operate the main valve directly, the solenoid opens and closes a pilot valve that requires relatively little power to operate. But the pilot valve controls flow of fluid under pressure in such a way as to direct the fluid pressure to operate a valve that requires much greater power to operate. So it is the fluid supply that supplies the energy needed to operate the main valve, and the solenoid can be relatively small and require relatively little power.
Various piece-part tolerances and the deformation can result in some variability in the position of the pilot body. This variability can cause resultant variability in the pilot-valve member""s stroke. In a low-power pilot valve even relatively small variations can affect timing or possibly sealing force adversely and even prevent the pilot valve from opening or closing at all. Although it may be possible to reduce this variability during manufacture by taking particular care, it is not typically practical to take such measures during field maintenance or replacement.
We have devised a way of eliminating this difficulty. Instead of first positioning a pilot-valve body with respect to the main valve and then so securing to the solenoid-containing operator assembly onto the main valve as to hold the pilot-valve body in place, we provide the operator assembly as a single assembly with the pilot-valve body and actuator. As will be seen below, this tends to minimize the pilot-valve-stroke variability that would otherwise afflict the system.